The Fischer-Tropsch synthesis reaction began in 1923 when German chemists Fischer and Tropsch developed a technique for producing synthetic fuels from synthesis gas by coal gasification. The Fischer-Tropsch synthesis reaction is a reaction wherein a synthesis gas is converted into a hydrocarbon by using a catalyst, and the catalyst used herein is that the higher selectivity of catalyst is the higher productivity of hydrocarbons having 5 or more carbon atoms, which is an index of general productivity, can be increased, thereby increasing the overall carbon efficiency.
As a material showing activity in the Fischer-Tropsch synthesis reaction, a group VIII metal material such as iron (Fe), cobalt (Co), nickel (Ni) and ruthenium (Ru) has been reported. Among them, iron (Fe) based catalysts are especially advantageous for the Fischer-Tropsch synthesis reaction associated with indirect coal liquefaction because of their low production cost, excellent performance, and activity in water-gas shift (WGS) reaction.
In Fe-based catalysts for FT synthesis reaction, Fe-based carbides such as ε′-F2.2C and χ-Fe2.5C are known as active species. However, since the Fe-based catalyst immediately after the production is mostly composed of Fe-based oxides, activation pre-treatment must be performed using a reducing gas including CO prior to the FT synthesis reaction.
In general, iron-based oxide catalysts are well-reduced in a reducing gas composed of CO regardless of pressure, but are not easily reduced in a high-pressure synthesis gas environment such as a Fischer-Tropsch synthesis reaction condition.
In addition, in the Fe-based catalyst, the Fe-based carbide, which is an active species, is highly possible to be re-oxidized and de-carburized by H2O and CO2 generated as byproducts during the FT synthesis reaction, development of highly reducible and highly carburizable catalysts is very important.